Room: Exhibit Hall | Forum 3
Purpose: Development of dose verification techniques is a much-needed improvement to verify delivered dose to small animal in preclinical radiation research. Since tumor response and normal tissue toxicity are radiation dose-dependent, dose verification allows users to quantify deviations of the delivered dose from the intended dose to ensure the accuracy and reproducibility of small animal radiation therapy. To measure delivered dose to small animal, we implement a real-time electronic portal imaging device (EPID) dosimetry in administered image-guided radiotherapy fraction for 20 rats with prostate cancer.
Methods: We previously calibrated in-built EPID on the small animal radiation research platform (SARRP, Xstrahl, Inc.) to measure two-dimensional (2D) dose distributions of kilovoltage (kV) x-ray beam at objectâ€™s exit surface. To verify the accuracy of delivered dose to the animal, we compared calculated dose distributions by the treatment planning system (TPS) (MuriPlan, Xstrahl, Inc.) as the planed dose, with real-time EPID-measured dose maps as the actual delivered dose. Accuracy of our EPID dosimetry technique was verified by comparison against film measurements during animal treatment.
Results: Comparison of central axis (CAX) dose rate values at exit surface of 20 rats showed that average differences between TPS and EPID were 0.06 cGy/s (3.08%), with maximum 0.18 cGy/s (9.3%). Gamma analyses for 2D exit dose verification between TPS-calculated and EPID-measured dose distributions showed average 90% passing rate with 2mm/5%. The accuracy of EPID measurements were also verified. The CAX dose values of EPID and film were in a close agreement in both the imager level and exit surface of animals, with average differences of 1% and 2%, respectively.
Conclusion: We implemented a real-time dosimetry technique using an EPID at kV x-ray energy to measure delivered dose to rat. This is an invaluable tool for verifying delivered dose to small animals in preclinical radiation research.